From Clipper yacht harbor in sausalito ( north end of the channel), it's still 10-15 minutes to open
water. THough in summer it can be sailed. Lots O dinghy's kayaks to dodge in the channel.
Other options are paradise cay marina on the east side of Tiburon and lock lommond in San Rafael. Paradise dumps right into the bay. Lock Lommond has a 20 minute
motor down the narrow channel San Rafael channel.
Added bonus they are some minutes closer then Sausalito. Last time I was in Sausolito all the marina's looked pretty full.
You might try brickyard cove in point Richmond as that's a nice area and saves a bridge toll and traffic on 101.